This enzyme was unique in its ability to efficiently cleave a broad range of salicylates, gentisates and 1-hydroxy-2-naphthoate in comparison with the more substrate-specific gentisate 1,2-dioxygenases (EC 1.13.11.4) and 1-hydroxy-2-naphthoate dioxygenase (EC 1.13.11.38). With the exception of 1-hydroxy-2-naphthoate dioxygenase, this enzyme differed from other ring fission dioxygenases in its ability to cleave substituted salicylates carrying a single hydroxy group. Such substrates are not activated for ring fission by other electron-donating substituents. It was also different from known gentisate 1,2-dioxygenases, or 1-hydroxy-2-naphthoate dioxygenase, in its ability to cleave salicylate, as well as its ability to efficiently cleave gentisate and 1-hydroxy-2-naphthoate. Gentisate 1,2-dioxygenases do not oxidize salicylate and 1-hydroxy-2-naphthoate dioxygenase does not oxidize salicylate or gentisate (in [Hintner04] and in [Matera08]).

Amino acid sequence comparisons showed 31% sequence identity between this enzyme and a gentisate 1,2-dioxygenase and 28% identity for a 1-hydroxy-2-naphthoate dioxygenase, suggesting that they are only distantly related to this enzyme [Hintner04].

The crystal structure of this homotetrameric enzyme has been determined at 2.9 Å resolution. It is a member of the type III extradiol-type dioxygenases. The catalytic center contained a mononuclear iron(II) coordinated to three histidine residues within the N-terminal domain. Active site residues responsible for the broad substrate specificity were identified [Matera08].
The subunit apparent molecular mass was determined by SDS-PAGE [Hintner01].
The gene has not been named and is referred to here by accession number.

In assays of cell extracts the enzyme was inhibited by Fe2+ chelators, suggesting Fe2+ as a cofactor [Hintner01].

For the purified enzyme, the higher Kcat/Km values for gentisate and 1-hydroxy-2-naphthoate suggested that these substrates were preferred over salicylate and the enzyme was concluded to be a gentisate 1,2-dioxygenase with a very broad substrate range [Hintner01].